{"paper":{"title":"Measurements of the UV background at 4.6 < z < 6.4 using the quasar proximity effect","arxiv_id":"1011.5850","primary_cat":"astro-ph.CO","submitted_at":"2010-11-26T17:57:15+00:00","version_compiled":"v1"},"notice":"Every quoted sentence is the authors' text from the arXiv listing abstract. Labels and probabilities are the outputs of classifier-1.13-20260917 on the question bank abstract-p1-20260923, exactly as returned. No sentence in this record was written by a language model.","schema":"pith.compiled-record/v0","status":"compiled","abstract":{"source":"arXiv listing abstract v1","sentences":[{"i":0,"p":1.0,"id":"s0","own":true,"role":"contribution","text":"We present measurements of the ionising ultraviolet background (UVB) at z ~ 5-6 using the quasar proximity effect.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.97,"main_claim_p":0.07,"quantitative":true,"quantitative_p":0.75,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":1.0,"interpretation":0.0}},{"i":1,"p":0.72,"id":"s1","own":true,"role":"contribution","text":"The fifteen quasars in our sample cover the range 4.6 < z_q < 6.4, enabling the first proximity effect measurements of the UVB at z > 5.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.93,"main_claim_p":0.04,"quantitative":true,"quantitative_p":0.98,"role_probabilities":{"gap":0.13,"method":0.15,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.72,"interpretation":0.0}},{"i":2,"p":1.0,"id":"s2","own":true,"role":"method","text":"The metagalactic hydrogen ionisation rate, Gamma_bkg, was determined by modelling the combined ionisation field from the quasar and the UVB in the proximity zone on a pixel-by-pixel basis.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.95,"main_claim_p":0.03,"quantitative":false,"quantitative_p":0.06,"role_probabilities":{"gap":0.0,"method":1.0,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":3,"p":1.0,"id":"s3","own":true,"role":"method","text":"The optical depths in the spectra were corrected for the expected effect of the quasar until the mean flux in the proximity region equalled that in the average Ly-alpha forest, and from this we make a measurement of Gamma_bkg.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.96,"main_claim_p":0.04,"quantitative":false,"quantitative_p":0.15,"role_probabilities":{"gap":0.0,"method":1.0,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":4,"p":0.98,"id":"s4","own":true,"role":"method","text":"A number of systematic effects were tested using synthetic spectra.","hedge":{"p":0.94,"label":"asserted"},"own_p":0.91,"main_claim_p":0.01,"quantitative":false,"quantitative_p":0.05,"role_probabilities":{"gap":0.0,"method":0.98,"result":0.0,"background":0.0,"limitation":0.01,"future_work":0.0,"contribution":0.01,"interpretation":0.0}},{"i":5,"p":0.58,"id":"s5","own":true,"role":"limitation","text":"Noise in the flux was found to be the largest source of bias at z ~ 5, while uncertainties in the mean transmitted Ly-alpha flux are responsible for the largest bias at z ~ 6.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.95,"main_claim_p":0.03,"quantitative":true,"quantitative_p":0.77,"role_probabilities":{"gap":0.0,"method":0.08,"result":0.32,"background":0.0,"limitation":0.58,"future_work":0.0,"contribution":0.01,"interpretation":0.01}},{"i":6,"p":0.59,"id":"s6","own":true,"role":"result","text":"The impacts of large-scale overdensities and Lyman limit systems on Gamma_bkg were also investigated, but found to be small at z > 5.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.96,"main_claim_p":0.02,"quantitative":false,"quantitative_p":0.47,"role_probabilities":{"gap":0.0,"method":0.31,"result":0.59,"background":0.0,"limitation":0.06,"future_work":0.0,"contribution":0.04,"interpretation":0.0}},{"i":7,"p":1.0,"id":"s7","own":true,"role":"result","text":"We find a decline in Gamma_bkg with redshift, from log(Gamma_bkg) = -12.15 $\\pm$ 0.16 at z ~ 5 to log(Gamma_bkg) = -12.84 $\\pm$ 0.18 at z ~ 6 (1 sigma errors).","hedge":{"p":1.0,"label":"asserted"},"own_p":0.98,"main_claim_p":0.7,"quantitative":true,"quantitative_p":0.99,"role_probabilities":{"gap":0.0,"method":0.0,"result":1.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":8,"p":0.51,"id":"s8","own":true,"role":"result","text":"Compared to UVB measurements at lower redshifts, our measurements suggest a drop of a factor of five in the HI photoionisation rate between z ~ 4 and z ~ 6.","hedge":{"p":1.0,"label":"hedged_possibility"},"own_p":0.79,"main_claim_p":0.22,"quantitative":true,"quantitative_p":0.99,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.51,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.49}},{"i":9,"p":0.73,"id":"s9","own":true,"role":"result","text":"The decline of Gamma_bkg appears to be gradual, and we find no evidence for a sudden change in the UVB at any redshift that would indicate a rapid change in the attenuation length of ionising photons.","hedge":{"p":0.99,"label":"asserted"},"own_p":0.96,"main_claim_p":0.15,"quantitative":false,"quantitative_p":0.08,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.73,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.27}},{"i":10,"p":1.0,"id":"s10","own":true,"role":"interpretation","text":"Combined with recent measurements of the evolution of the mean free path of ionising photons, our results imply decline in the emissivity of ionising photons by roughly a factor of two from z ~ 5 to 6, albeit with significant uncertainty due to the measurement errors in both Gamma_bkg and the mean free 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